Compressed gas tank system with fast fueling ability at any vessel pressure

ABSTRACT

A method of fueling with compressed gas is described. In one embodiment, the method includes providing a supply of compressed gas; providing a storage tank with a fueling line, and a nozzle in the fueling line, the nozzle movable between at least a flow reduction position and a full fuel flow position; initiating fueling from the supply of compressed gas with the nozzle in the flow reduction position for a predetermined time or until a minimum pressure is obtained; when the predetermined time or the minimum pressure is obtained, moving the nozzle to the full fuel flow position; and fueling the storage tank from the supply of compressed gas with the nozzle in the full fuel flow position until fueling is completed. A vehicle incorporating the nozzle is also disclosed.

BACKGROUND OF THE INVENTION

The invention relates generally to fueling of compressed gas tanks, andmore particularly, to methods and apparatus for safe fueling ofcompressed gas tanks.

A key component in a high pressure storage system for vehicleapplications, such as hydrogen, or compressed natural gas (CNG), is thetank vessel. One type of tank vessel for storing compressed gas is amade of a fiber composite. Fiber composite vessels are desirable becausethey have a good storage to weight ratio. They typically have twolayers: an outer layer, made of a carbon fiber matrix for example, thatis designed to bear the mechanical load, and an inner layer, or liner,made of a bubble of plastic or aluminum, that is designed to preventleaking.

The geometry of the inner liner and the fiber matrix layer are usuallydifferent for material and process reasons. The inner layer generallycannot withstand stress forces. To ensure that the liner is firmlysupported by the outer layer, a minimum pressure should be maintained atall times. At pressures below the minimum pressure, for example lessthan about 20 bar, the two layers may separate from each other. If fuelis introduced into the vessel quickly under high pressure below theminimum pressure, the inner liner will bump against the fiber matrixlayer very hard. The liner could rupture, and the contents would flowthrough the outer layer into the environment. In addition, gas trappedin the gap between the two layers can damage the liner and/or the fibermatrix layer.

Tank pressure evaluation has a certain tolerance, which increases overtime. For example, the tolerance chain is the sum of several componentsand the converter. The tolerance for the P-transducer includes the A/Dconverter, the temperature compensator, and the D/A converter, whichcould be ±13.5 bar, for example. The tolerance for the vehiclecontroller could be ±18 bar, for example. Thus, the signal tolerancewould be 31.5 bar, for example. The degradation over time needs to beconsidered also, which could be ±2.25 bar/yr, for example. Thus, for a 4year old p-transducer, the tolerance would be the sum of these, or ±40.5bar, for example.

The worst case tolerance margin has to be added to the signal tolerancealong with a safety margin. Thus, for reasons of safety, hydrogenrelease may need to be stopped at a tank pressure of 65 bar by thevehicle controller (e.g., 20 bar minimum pressure+31.5 signaltolerance+9 bar degradation+4.5 bar safety margin=65 bar). However, atthe calculated shutdown pressure, the “real” tank pressure could be anyvalue between 20 bar and 105 bar, as shown in FIG. 1. Therefore, in allnon-worst case situations, the worst case tolerance margin results in areduced usable hydrogen mass and thus a reduced vehicle range of up to14%.

Typically, the driver of the vehicle fuels at a filling station. Somefueling stations have the ability to recognize the vessel filling grade,while others do not. If the fueling station has an infrared (IR)interface, a computer, and mapping, the fueling station can control theproper fueling. The vehicle storage tank is connected to the fillingnozzle of the station and creates a “short cut” between the empty vesseland the 875 bar pressure of the station. The “short cut” between theempty vessel and the 875 bar source creates a very strong pressure jumpand very high gas flow. A slow fill has a reduced flow compared with theregular fast fill. Presently, slow fill is only possible at a servicehub with trained personnel and special equipment (H₂ bottle, flowrestrictor, pressure gauge).

Furthermore, it is believed that fast filling has been done improperlyin some situations, e.g., without knowledge, without tracing, and/orwithout instrumentation.

SUMMARY OF THE INVENTION

One aspect of the invention is a method of fueling with compressed gas.In one embodiment, the method includes providing a supply of compressedgas; providing a storage tank with a fueling line, and a nozzle in thefueling line, the nozzle movable between at least a flow reductionposition and a full fuel flow position; initiating fueling from thesupply of compressed gas with the nozzle in the flow reduction positionfor a predetermined time or until a minimum pressure is obtained; whenthe predetermined time or the minimum pressure is obtained, moving thenozzle to the full fuel flow position; and fueling the storage tank fromthe supply of compressed gas with the nozzle in the full fuel flowposition until fueling is completed.

Another aspect of the invention is a vehicle fueled by compressed gas.In one embodiment, the vehicle includes a fuel tank with a fueling line,a nozzle in the fueling line flow, the nozzle movable between at least aflow reduction position and a full fuel flow position, and a controllercontrolling the nozzle.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a graph showing the amount of range lost as a function of thepressure in the vessel.

FIG. 2 is an illustration of the one embodiment of the invention.

FIG. 3 is a graph showing a comparison of the current fueling processand the fueling process according to the present invention.

DETAILED DESCRIPTION OF THE INVENTION

The present invention provides a safe pressure increase in all fuelingsituations because the vehicle controls the filling mode, rather thanthe fueling station. Below a minimum pressure level, a slow fill isdone. A valve restricts the filling with a defined orifice. The slowfilling is done for a specified period, for example about 20 seconds, oruntil a minimum pressure is obtained. After that, the fast fill follows.In cases without knowledge of the vessel filling, the slow fill is doneautomatically. If the storage vessel has the required minimum pressurelevel initially, the fast fill can be done from beginning.

The present invention can provide safe fueling in situations including,but not limited to, very low pressure situations, where the fillinggrade of the vessels is not known, and fueling stations with damagedcommunication between the vehicle and the refueling station.

The present invention can have one or more advantages. It can providesafe fueling at any pressure, not only above the minimum pressure.Consequently, the driving range can be increased, e.g., up to about 14%.The tolerance chain of p-signal has no effect on the present invention.Regular fueling operation can be used, even if driver runs the vehiclebeyond the low level warning so that there is less than the minimumpressure. There are fewer requirements for the fueling station becauseslow and fast fueling are controlled by the vehicle, not the fuelingstation. Slow fill is permitted on any fueling station; no trainedpersonnel or special equipment are required. At the beginning offueling, the flow restrictor reduces the flow at low pressure for apredetermined time or until a minimum pressure is obtained. However, thefueling time will increase slightly, and an additional nozzle andoptional associated controls are required.

As illustrated in FIG. 2, the vehicle is fitted with a vehiclecontroller 30, a storage tank 35 having a liner 40 therein, a nozzle 10in the fueling line 15 that can switch between at least a flow reductionposition 20 and a full fueling flow position 25. The nozzle is behindthe back pressure valve which is closed by back pressure and opened byflow during fueling. The nozzle can be spring loaded or powered, forexample. With a spring loaded nozzle, the default position when theactuator is not energized is the flow reduction position. A powerednozzle will open and close on command. The unpowered position would bethe flow reduction position. For flow reduction, the orifice iscalibrated so that the pressurization of the tank 35 of the tank systembeginning from the lowest shutdown pressure (e.g., 5 bar) with fullsupply pressure (e.g., 800 bar) allows a slow pressurization to theminimum pressure where a flow reduction during fueling is not necessary(e.g., 20 bar) in a specified time (e.g., about 20 sec.) (seecalculation below). When fueling is detected or the tank pressure forhigh rate fueling is reached, the vehicle controller 30 switches thevalve from the flow reduction position to the full fueling flowposition. The valve can be a two position valve as described above.Alternatively, the valve could have one or more additional positions,such as a shut-off position, if desired. Alternatively, the valve couldbe a proportional flow reduction valve, in which the orifice can bevaried from at least a flow reduction position to a full flow position.The orifice could also act as a shutoff valve and completely close theflow.

The damage caused by improper fueling can be prevented. When the vehiclecontroller 30 is not in the fueling mode, the nozzle is set to the flowreduction position, and remains there throughout fueling. No linerdamage is possible because the fueling is very slow.

In all other fueling modes, the vehicle controller 30 will be in thefueling mode. Fueling is started at a low pressure condition with thenozzle in the flow reduction position for a specified time (e.g., 20sec) or until the desired pressure level is reached. The vehiclecontroller 30 detects fueling by pressure rise. There can be severalpressure sensors in the storage tank 35. An increase in the pressure isdetermined by the vehicle controller 30 independent of the pressuresignal tolerances. The tolerance on the pressure “movement” is much lessthan the absolute tolerance issue. When the time for safe pressure riseat low pressures is reached or when the pressure sensor indicates thatthe tank pressure is above the minimum pressure for high flow fueling,then the vehicle controller 30 will switch the valve to the full fuelingflow position. The pressure increase in an empty vessel is not done inone large pressure jump from low pressure with full flow to highpressure. The flow peak at the beginning of fueling is reduced, whichreduces the noise of fueling. The increase in mechanical stress from anessentially stressless situation to a high stress situation is stretchedinto a longer time frame.

Fueling can continue until it is completed, The fueling station cansignal that the tank 35 is full and end fueling. Alternatively, thecustomer can stop or interrupt fueling at any time. There will be noliner damage, and the fueling time is minimized (the time is increasedonly by the amount of the initial slow fill time if any).

FIG. 3 shows a comparison of fueling under the present system andfueling using the flow reduction nozzle of the present invention. Thetime increase for fueling is about 20 seconds (or some otherpredetermined time period).

The size of the orifice can be determined as follows:

-   Select the lowest assumed tank pressure—e.g., 5 bar-   Select the pressure level for full flow fueling—e.g., 20 bar-   Density difference at the temperature—e.g., 20° C.−1.5 g/l-   Tank volume—e.g., 117 l-   Determine amount of H₂—e.g., about 180 g-   Choose time to pressurize slowly—e.g., 20 sec-   Fueling Pressure—800 bar-   Determine flow reduction orifice—about 0.5 mm

Although the discussion above referred to storage tanks 35 for vehicles,one of skill in the art will recognize that the invention applies to anycompressed gas storage and refilling application whether mobile orstationary.

It is noted that terms like “preferably,” “commonly,” and “typically”are not utilized herein to limit the scope of the claimed invention orto imply that certain features are critical, essential, or evenimportant to the structure or function of the claimed invention. Rather,these terms are merely intended to highlight alternative or additionalfeatures that may or may not be utilized in a particular embodiment ofthe present invention.

For the purposes of describing and defining the present invention it isnoted that the term “device” is utilized herein to represent acombination of components and individual components, regardless ofwhether the components are combined with other components. For example,a “device” according to the present invention may comprise anelectrochemical conversion assembly or fuel cell, a vehicleincorporating an electrochemical conversion assembly according to thepresent invention, etc.

For the purposes of describing and defining the present invention it isnoted that the term “substantially” is utilized herein to represent theinherent degree of uncertainty that may be attributed to anyquantitative comparison, value, measurement, or other representation.The term “substantially” is also utilized herein to represent the degreeby which a quantitative representation may vary from a stated referencewithout resulting in a change in the basic function of the subjectmatter at issue.

Having described the invention in detail and by reference to specificembodiments thereof, it will be apparent that modifications andvariations are possible without departing from the scope of theinvention defined in the appended claims. More specifically, althoughsome aspects of the present invention are identified herein as preferredor particularly advantageous, it is contemplated that the presentinvention is not necessarily limited to these preferred aspects of theinvention.

What is claimed is:
 1. A method of reducing rupture damage to a liner ofa fuel cell tank during fueling with compressed gas comprising:providing a supply of compressed gas; providing a storage tank definingthe liner therein with a fueling line, and a nozzle in the fueling line,the nozzle movable between at least a flow reduction position and a fullfuel flow position; providing a controller configured to determine acalculated tolerance margin comprising a minimum pressure, a signaltolerance, a degradation and a safety margin; using the calculatedtolerance margin in conjunction with the controller to initiate a lowpressure fueling from the supply of compressed gas with the nozzle inthe flow reduction position until the minimum pressure of approximately20 bar within the storage tank is obtained after which the nozzle ismoved to the full fuel flow position to deliver a high pressure fueling;fueling the storage tank from the supply of compressed gas with thenozzle in the full fuel flow position until fueling is completed whereinthe initiating of the low pressure reduces a tendency of the liner torupture through lower impact force between the liner and a surface ofthe fuel cell tank.
 2. The method of claim 1 further comprisinginitiating fueling from the supply of compressed gas with the nozzle inthe flow reduction position and maintaining the nozzle in the flowreduction position until fueling is completed.
 3. The method of claim 1wherein the nozzle is spring loaded.
 4. The method of claim 1 whereinthe nozzle is powered.
 5. The method of claim 1 wherein the nozzle is aproportional flow reduction valve.
 6. The method of claim 1 whereinmoving the nozzle is controlled by the controller.
 7. The method ofclaim 1 wherein storage tank is in a vehicle and wherein the compressedgas is hydrogen or natural gas.
 8. A method of reducing rupture damageto a liner of a fuel cell tank during fueling with compressed gascomprising: providing a supply of compressed gas; providing a storagetank defining a liner therein with a fueling line, a nozzle in thefueling line, the nozzle movable between at least a flow reductionposition and a full fuel flow position; providing a controllerconfigured to determine a calculated tolerance margin comprising aminimum pressure, a signal tolerance, a degradation and a safety marginand for controlling the nozzle; using the calculated tolerance margin inconjunction with the controller to initiate a low pressure fueling fromthe supply of compressed gas with the nozzle in the flow reductionposition until the minimum pressure of approximately 20 bar within thestorage tank is obtained after which the nozzle is moved to the fullflow position to deliver a high pressure fueling; determining if apressure exceeds the minimum pressure; if the pressure exceeds theminimum pressure, moving the nozzle to the full fuel flow position todeliver a high pressure fueling, and initiating fueling from the supplyof compressed gas with the nozzle in the full fuel flow position untilfueling is complete; if the pressure does not exceed the minimumpressure, initiating the low pressure fueling from the supply ofcompressed gas with the nozzle in the flow reduction position until theminimum pressure is obtained; when the minimum pressure is obtained,moving the nozzle to the full fuel flow position to deliver the highpressure fueling; and fueling the storage tank from the supply ofcompressed gas with the nozzle in the full fuel flow position untilfueling is completed wherein initiating the low pressure reduces atendency of the liner to rupture through lower impact force between theliner and a surface of the fuel cell tank.
 9. The method of claim 8wherein the nozzle is spring loaded.
 10. The method of claim 8 whereinthe nozzle is powered.
 11. The method of claim 8 wherein the nozzle is aproportional flow reduction valve.
 12. The method of claim 8 whereinstorage tank is in a vehicle and wherein the compressed gas is hydrogenor natural gas.
 13. A vehicle fueled by hydrogen to reduce rupturedamage to a liner of a fuel tank comprising: the vehicle having the fueltank defining the liner therein with a fueling line, a nozzle in thefueling line flow, the nozzle movable between at least a flow reductionposition and a full fuel flow position, and a controller configured todetermine a calculated tolerance margin comprising a minimum pressure, asignal tolerance, a degradation and a safety margin and for controllingthe nozzle wherein the calculated tolerance margin is used inconjunction with the controller to initiate a low pressure fueling froma supply of hydrogen with the nozzle in the flow reduction positionuntil the minimum pressure of approximately 20 bar within the fuel tankis obtained after which the nozzle is moved to the full fuel flowposition to deliver a high pressure fueling until fueling is completewherein the initiating of the low pressure reduces a tendency of theliner to rupture through lower impact force between the liner and asurface of the fuel tank.
 14. The vehicle of claim 13 wherein the nozzleis spring loaded.
 15. The vehicle of claim 13 wherein the nozzle is aproportional flow reduction valve.
 16. The vehicle of claim 13 whereinthe fuel tank further comprises an outer layer made of a composite. 17.The vehicle of claim 16 wherein the composite is a carbon fiber matrixand wherein the liner is plastic or aluminum.
 18. The vehicle of claim13 wherein the nozzle is powered.